Demonstration of high porosity cooling systems using novel Thermochromic Liquid Crystal approach

Abstract

High porosity cooling systems have recently shown promise as a potential option for increasing turbine blade cooling effectiveness. To demonstrate the viability of this approach, a set of turbine blades with a double wall high porosity cooling scheme was manufactured from engine-grade materials. These were tested for metal effectiveness at steady state using a lowtemperature high-speed cascade with engine-representative conditions.Metal effectiveness values were obtained using a novel post-processing technique, based on the response of multiple narrow-band liquid crystals allowing for high-resolution in situ measurements.Results demonstrated the high cooling potential of such designs as well as their potential implementation within a double-walled system. The comparison between the measured metal effectiveness values to existing state of the art cooling designs suggests that the potential increase in cooling effectiveness exceeds 5-7% at existing mass flows or alternatively, allows for a 15-20% reduction in coolant mass flow for equivalent cooling effectiveness levels. KEYWORDSMETAL EFFECTIVENESS, TRANSPIRATION COOLING, HIGH POROSITY, DOUBLE WALL COOLING, TLCS NOMENCLATURE BR Blowing ratio D Film hole diameter (mm) h heat transfer coefficient (HTC) (W/m 2 .K) i Pixel relative intensity k Metal Conductivity (W/m.K) L Pressure surface length (mm) M* nondimensional mass flow rate .𝑚 ̇𝑐 Coolant mass flow rate PR Pressure Ratio